Refining mineral oil with molten caustic and adsorbent



April 16, 1957 l. W. MILLS REFINING MINERAL OIL WITH MOLTEN CAUSTIC ANDADSORBENT Crude Nuphthenic Petroleum Gus Oil and Lighter t/m ToppingStill Fig. 2

Crude T p e 3 Filed June 2, 1954 Fig Lubricating Oils . l8 l9Distillation Adsorbem Zone 9 ll FIG 2 Residue Finished HenvyLubricantuooo- 12,000 BBL/Ton of Adsorbent) ,2? l7 Lubricating Oils,Etc.

l8 Oondensote Containing 26 l-200 PPM of Sodium 24" 29 ;& L Alkali 22 7.A|kcn so INVENTOR. IVOR W. MILLS IG l I Residue ATTO NEY nited Statsatent 1 REFINING MINERAL OIL WITH MOLTEN CAUSTIC AND ADSORBENT Ivor W.Mills, Glenolden, Pa., assiguor to Sun Oil Company, Philadelphia, Pa., acorporation of New Jersey Application June 2, 1954, Serial No. 433,945

5 Claims. (Cl. 196-36) This invention relates to the refining of mineraloil, and more particularly to the improving of certain products obtainedin the vapor phase treatment of mineral oil with caustic alkali.

It is known in the art to refine mineral oil, for example lubricatingoil, by vaporizing the oil and contacting the vapors with a causticalkali, for example aqueous caustic soda or potash, molten anhydroussodium or potassium hydroxide, etc. Such treatment has been employed forexample in the refining of naphthenic mineral oils in order to removenaphthenic acids by reaction with sodium hydroxide to form sodiumnaphthenates in the alkaline treating agent; such sodium naphthenatescan be recovered by known methods from the alkaline treating agent toobtain a valuable article of commerce. The mineral oil vapors, aftercontact with caustic alkali, are generally subjected then tofractionation by known means to obtain various lubricating oilcondensates of varying boiling range. These lubricating oils are usefulin various applications, and the heaviest of these lubricating oils haventunerous applications, for example in greases, as electrical oils, gearlubricants, etc.

As previously practiced the vapor phase treatment with caustic alkalihas commonly been accomplished in a distillation tower containing acaustic treating section and a fractionating section thereabove. Inprior art operation the vapors pass from the uppermost tray or bubbleplate in the caustic treating section upwardly into the fractionationsection, and means may be provided to avoid entrainment of alkalinematerial from the caustic treating section. In order to avoid suchentrainment a fractionating tray or trays maybe provided between theuppermost tray of the caustic treating section and the tray from whichthe heaviest lubricant product is removed; alternatively, or inaddition, a metal screen of known type may be employed in the towerbetween the caustic treating section and the fractionation section.

In spite of these precautions, it is not infrequently found that theheaviest lubricant product obtained fromthe fractionation section hasunsatisfactory quality from various standpoints, for example poorelectrical resistivity. It has been found that such poor properties areattributable to the fact that very small amounts of sodium hydroxide orother alkali-metal containing materials become incorporated in theheaviest lubricant product, having been carried to the fractionationsection by entrainment in spite of the precautions taken. It may also befound in some instances that more than one of the heavy lubricantproducts contains some small amounts of alkali metal compounds; however,it is most frequently the heaviest lubricant product which is thusaffected.

The problem of entrainment, and the consequent problem of alkali metalcontent in the heavy lubricants isv a particularly diflicult one, inview of the various means which have been employed to avoid entrainment,without success in completely avoiding the presence of alkali metal inthe heaviest lubricants. Various means which have been employed to avoidentrainment have probably been regarded heretofore as providingsubstantially com plete prevention of entrainment. However, the presenceof small amounts of alkali metal, producing deleterious effects in theheaviest lubricants, indicates that the removal has not been complete byprior art methods.

According to the present invention, heavy lubricants produced by a vaporphase refining with caustic alkali are produced in a manner such thatthe alkali metal content of the lubricant is well within the limitsrequired for most or all of the uses of such lubricants. Thus thepresent invention enables the obtaining of an alkali metal content whichis satisfactory when the lubricant is used as an electrical oil, thestandards being quite strict for such oils since the resistivity of theoil is adversely aiiected by the presence or" alkali metal in the oil.

The treatment according to the invention involves, in one embodiment,the contacting of a heavy lubricant obtained in a vapor phase refiningprocess, which lubricant contains 1 to 200 parts per million of alkalimetal in the form of alkali metal compounds, with bauxite underconditions as subsequently specified. It has been found that suchcontacting is capable of reducing the alkali metal content to a very lowlevel in an operation which provides a very high yield of finishedlubricant oil per unit amount of bauxite employed.

The invention will be further described with reference to the attacheddrawing. Figure 1 illustrates the principal steps involved in a typicalembodiment of the process of the invention. Figure 2 illustrates in moredetail the steps involving the vapor phase treatment of oil with alkaliand fractionation of the treated oil.

Referring to Figure l, a crude naphthenic petroleum is introducedthrough line 13 into a topping still 10 wherein the gas oil and lighterfractions are distilled from the crude and removed as indicatedschematically by line 14. Topped crude is removed from the still throughline 15 and introduced into the vapor phase alkali treating zone 11,into which alkali is introduced through line 29, and from whichlubricating oil distillates and residue are removed respectively throughlines 17 and 16. A heavy lubricating oil fraction, boiling higher thanthe oils removed as indicated at line 17, is removed through line 13 andintroduced into adsorbent treating Zone 12, wherein it is contacted withbauxite in order to remove the small amounts of alkali metal whichbecame incorporated in the heavy lubricant during the treatment in zoneii. The heavy lubricant obtained by the bauxite treatment is removedthrough line 19. As indicated in the drawing the yields of heavylubricant obtained are within the range from 1000 to 12,000 barrels ofoil per ton of bauxite.

Referring now to Figure 2, the vapor phase alkali treating zone isillustrated in more detail as a distillation tower containing a flashzone 31, an alkali treating zone comprising the trays 20, 21 and 22, anintermediate zone comprising the trays 23 and 25 and the screen 24, anda fractionation section comprisingthe trays 26, 27 and 2S.

Preheated topped crude is introduced through line 15,

30. The vapors rising through the caustic treating section 3 come incontact with the alkali on the trays, and the refining action of thelatter takes place. A portion of the alkali removed through line 30 maybe subsequently treated by methods known in the art for removal ofsodium naphthenates, etc., and a portion of the. alkali removed may berecycled to the caustic treating section through line 29.

The vapors rising above tray 22 pass through tray 23, on which theliquid is primarily oil, and then passes through the screen 24, whichmay be any suitable type of screen, or demistcr, as known in the art,for minimizing entrainment in distillation towers. The vapors then passthrough tray 25, on which the liquid is primarily oil, and then throughtray 26 from which the heaviest lubricant product from the fractionationsection is removed through line 18.

The lubricant removed through line 18 contains 1 to 200 p. p. m; ofsodium which has become incorporated in the lubricant because ofentrainment of sodium-containing materials by the oil vapors as theypass from the caustic treating section into the fractionation section.The various sodium-containing materials in the heavy lubricant mayinclude sodium naphthenate, sodium hydroxide, sodium carbonate, etc. Thelighter vapors pass upwardly from tray 26 to the other trays of thefractionation section, which may be any suitable number, and as shown inthe drawing include trays 27 and 28. From these various additional traysof the fractionation section the lighter lubricating oils are removedthrough line 17.

The heavy lubricant removed through line 18 is treated, as described inconnection with Figure 1, with bauxite in order to remove nearly all ofthe sodium contained therein.

The following examples illustrate the process of the invention.

7 Example I A process according to the general scheme indicated inFigures 1 and 2 was carried out under the following conditions. T .ebauxite which was employed was a lowiron bauxite containing 75 to 82%alumina, 10 to 14% silica, 2.5 to 3.5% ferric oxide and 3.5 to 4.5%titanium oxide; the bauxite, according to manufacturers specifications,contained 2.9% free moisture (determined by heating to 220 F. for 2hours) and had an ignition loss after 2 hours at 1800 F. of 5.2%. Thisbauxite was employed in a bed which was preheated above 220 F. to removefree moisture. A heavy lubricant condensate obtained as indicated inFigure 2 of the drawing was then percolated through the bed in acontinuous process running for 15 days. The bauxite employed consistedmainly of particles from 10 to mesh. The sodium content, as determinedin the Bcckman flame photometer, of the lubricant prior to treatmentwith bauxite varied from 16 to 108 p. p. m. during the 15 day period,and the average sodium content was about 55 p. p. m. About 85% of thesodium was present in the form of sodium naphthenate, and 12% as sodiumhydroxide, the remainder probably being sodium carbonate. The space ratein the percolation was about 2 volumes of oil per volume of bauxite perhour. The average temperature of the oil upon introduction into the bedwas about 480 F. After about 10 days, during which 2500barrels of oilper ton of bauxite had been passed through the bauxite, the sodiumcontent of the bauxite-treated oil was 5 p. p. m., indicating a highlysatisfactory removal of sodium from the oil.

Example 11 In an operation generally similar to that described inExample I, a bed of bauxite was employed for a two month period, duringwhich time the sodium content of the heavy lubricant prior to thebauxite treatment was in the neighborhood of 10 p. p. m. throughout theperiod. The sodium content of the treated oil was approximately 4 l p.p. in. during the two months period, and the yield of oil obtained wasin the neighborhood of 10,000 barrels per ton of bauxite.

The treatment according to the invention generally involves only slight,if any, decolorizing of the mineral oil treated, and the adsorbent isgenerally used for considerably longer periods of time and for treatmentof considerably greater amounts of mineral oil than are possible when adecolorizing action is effected. Thus for example in a treatment withbauxite at 550 F., after treatment of 3500 barrels of oil per ton ofbauxite, the color of the product was not improved over the color of thecharge to the bauxite treatment and was instead very slightly poorerthan the initial color.

The temperature of the treatment according to the invention can vary.The temperature should be high enough to obtain a suitabie fluidity ofthe mineral oil and efiectiyeness of the bauxite, but should not be sohigh as to cause any substantial cracking of the oil. Temperatureswithin the approximate range from 350 F. to.600 'F. are generallysuitable; preferred temperatures are those in the range from 450 F. to550 F. Preferred space rates are those in the range from 0.1 to 5volumes of oil per volume of adsorbent per hour.

A preferred manner of effecting the adsorbent treatment according to theinvention is to percolate the liquid mineral oil through a stationarybed of adsorbent particles. in such operation the particle size of theadsorbent should not be so small as to cause a disadvantageously highpressure drop during passage of the oil through the bed. Generally it ispreferred that a major proportion of the particles in the bed should bebetween 10 to 60 mesh in size.

A bauxite containing less than about 10 percent by weight ferric oxidecan be advantageously used according to the invention, but bauxitecontaining greater amounts of ferric oxide, e. g. 14 percent or more,can also be used with entirely satisfactory results.

The bauxite adsorbent, after use in removing alkali metal compounds fromoil, can be regenerated for further such use by contact with a acidicregenerating agent, e. g. dilute mineral acid such as hydrochloric acid,sulfuric acid, etc. However the life obtainable without regeneration isquite long, as previously pointed out, and it may be unnecessary orundesirable to regenerate the adsorbent.

The oil treated according to the invention should contain 1 to 200 p. p.m. of alkali metal prior to the adsorbent treatment. Oils containingless than 1 p. p. m. of alkali metal generally do not require anyfurther treatment for removal of alkali metal. Oils containing more than200 p. p. m. of alkali metal, on the other hand, tend to deactivate theadsorbent too rapidly for satisfactory operation. Therefore the vaporphase alkali treatment prior to the adsorbent treatment should becarried out in such a way as to produce a heavy condensate containingless than 200 p. p. m. alkali metal initially. V

In place of bauxite, activated alumina can be used as adsorbentaccording to the invention; however, activated alumina has aconsiderably shorter life than bauxite, since it is more readilydeactivated during the treatment.

The treatment according to the invention may'advantageously be appliedto oils having S. U. viscosity at 210 F. within the approximate rangefrom 75 to 200 seconds, and preferably from to seconds.

The treatment according to the invention may advantageously be used incases where the oil is subsequently treated with a catalyst which issubject to poisoning by alkali metal compounds, as in the case of acatalyst comprising molybedenum sulfide or other sulfactivehydrogenation catalyst precipitated on alumina or bauxite, etc. 1

The invention claimed is;

1. Process for refining mineral oil which comprise vaporizing mineraloil; contacting the evolved vapors containing naphthenic acids withmolten anhydrous caustic alkali in a contacting zone; passing thecontacted vapors from said contacting zone into a fractionating zone;condensing in said fractionating zone as heaviest distillate product aheavy lubricating oil containing 1 to 200 p. p. m. of alkali metal inthe form of alkali metal compounds; percolating said heavy lubricatingoil at a temperature within the approximate range from 350 F. to 600 F.through a bed of bauxite at a space rate of 0.1 to 5 volumes of oil pervolume of bauxite per hour to remove alkali metal compounds from saidcondensate; and continuing said percolating during a period in which theelectrical resistivity of the oil is improved.

independently of color improvement, at least 1000 barrels of condensatebeing treated per ton of bauxite.

2. Process according to claim 1 wherein said condensate, prior tocontacting with bauxite, contains about 5 to 50 p. p. m. or alkalimetal.

3. Process according to claim 1 wherein said caustic alkali is causticsoda.

4. Process according to claim 1 wherein said bauxite contains a majorproportion of 10 to 60 mesh particles.

5. Process for refining mineral lubricating oil which and at a spacerate of 0.1 to 5 volumes of oil per volume of bauxite per hour; andcontinuing said percolating during a period in which the electricalresistivity of the oil is improved independently of color improvement,1000 to 12,000 barrels of said heavy lubricant being treated per ton ofsaid bauxite.

References Cited in the file of this patent UNITED STATES PATENTS1,698,076 Taber Jan. 8, 1929 2,340,939 Davis et a1 Feb. 8, 19442,658,027 Hoover Nov. 3, 1953

1. PROCESS FOR REFINING MINERAL OIL WHICH COMPRISES VAPORIZING MINERALOIL; CONTACTING THE EVOLVED VAPORS CONTAINING NAPHTHENIC ACIDS WITHMOLTEN ANHYDROUS CAUSTIC ALKALI IN A CONTACTING ZONE; PASSING THECONTACTED VAPORS FROM SAID CONTACTING ZONE INTO A FRACTIONATING ZONE;CONDENSING IN SAID FRACTIONATING ZONE AS HEAVIEST DISTILLATE PRODUCT AHEAVY LUBRICATING OIL CONTAINING 1 TO 200 P.P. M. OF ALKALI METAL IN THEFORM OF ALKALI METAL COMPOUNDS; PERCOLATING SAID HEAVY LUBRICATING OILAT A TEMPERATURE WITHIN THE APPROXIMATE RANGE FROM 350*F. TO 600*F.THROUGH A BED OF BAUXITE AT A SPACE RATE OF 0.1 TO 5 VOLUMES OF OIL PERVOLUME OF BAUXITE PER HOUR TO REMOVE ALKALI METAL COMPOUNDS FROM SAIDCONDENSATE; AND CONTINUING SAID PERCOLATING DURING A PERIOD IN WHICH THEELECTRICAL RESISTIVITY OF THE OIL IS IMPROVED INDEPENDENTLY OF COLORIMPROVEMENT, AT LEAST 1000 BARRELS OF CONDENSATE BEING TREATED PER TONOF BAUXITE.